This disorder, which is called "stress cardiomyopathy" or "broken heart syndrome," is most common in older women, typically striking after a major physical strain like surgery or mental hardship like the death of a loved one.

Now a new study, one of the largest of its kind, confirms that stress cardiomyopathy can also affect men and premenopausal women.

And in as many as one-third of cases, a triggering event cannot be pinpointed, suggesting that causes of stress cardiomyopathy may sometimes be too subtle to recognize.

Experts who were not involved in the research praised the study for its size and for its use of cardiac magnetic resonance imaging (MRI) scans to carefully document the physical features of the poorly understood syndrome.

"It was nice that they were able to get a big cohort of patients from different centers and kind of do things all the same way," says Mazen Hanna, MD, a cardiologist who is director of the heart failure intensive care unit at Cleveland Clinic in Ohio. "Kudos to them for pulling that off."

Others agree.

"I think it's the best large-scale study looking at the MRI features of this condition," says Ilan S. Wittstein, MD, a cardiologist and assistant professor at The Johns Hopkins University School of Medicine,in Baltimore.

"This definitely shows, using MRI, that the pathophysiology of this condition is very different," Wittstein tells WebMD. "It clearly separates this from other kinds of heart muscle disorders."

The study is published in the Journal of the American Medical Association.

Documenting Broken Heart Syndrome

Researchers in Germany and Canada identified 256 cases of stress cardiomyopathy between January 2005 and October 2010 from seven different hospitals in Europe and North America.

Patients ranged in age from 30 to 90. The average age was 69.

As expected, most of the affected patients, 81%, were postmenopausal women. But 8% of cases were in women younger than age 50, and 11% occurred in men.

Only two-thirds of study participants were able to identify something that triggered their symptoms.

For 30%, the cause was emotional, and included the death of a friend, pet, or relative, interpersonal conflict, anxiety, anger, or the loss of a job.

For 41% of study participants, the cause was physical. Top physical stressors reported in the study included surgery, breathing trouble like COPD, asthma, or bronchitis, and chemotherapy.

"Thus, our large multi-center cohort demonstrates that the absence of an identifiable stressful event does not rule out the diagnosis," they conclude, and surmise that the mysterious disorder may have complex underpinnings, involving the endocrine, vascular, and central nervous systems. This suggests the need for enhanced awareness and recognition of this condition to ensure correct diagnosis and management.

How Stress Cripples the Heart

Stress cardiomyopathy is thought to be at work in as many as 2% of people who are admitted to the hospital for a heart attack. Among women, that number is even higher, accounting for as many as 5% to 7% of those with suspected heart attacks, Wittstein says.

Though the mechanism isn't clear, researchers say it looks as though a surge in stress hormones causes blood vessels around the heart to constrict.

"When the very tiny blood vessels, the microvascular circulation, when that is affected, it can cause a temporary decrease in blood flow to the heart and cause a temporary stunning of the heart muscle," Wittstein says.

But unlike a heart attack, where heart cells actually die and there's scar tissue left, with stress cardiomyopathy, the heart muscle cells are temporarily stunned, but not irreversibly damaged.

"The heart muscle can look very weak at the time of [hospital] arrival, but it recovers completely," he says.

Most patients in the study presented with classic heart attack symptoms like chest pain and shortness of breath, but others were evaluated after they fainted or their heart suddenly stopped beating.

A few patients were admitted to the hospital after doctors suspected heart problems during other kinds of routine procedures.

All study participants had coronary angiograms, minimally invasive procedures that allow doctors to look for blocked arteries around the heart that may have caused a heart attack.

But those angiograms showed that 75% of patients in the study had healthy coronary arteries.

Others had blockages that were either too minimal or were in the wrong place to be causing their symptoms.

None had evidence of recently ruptured plaques, another hallmark of a heart attack.

Doctors could also see that the heart's main pumping chambers were weakened and distended, causing them to balloon when filled with blood.

All cases were then evaluated with cardiac magnetic resonance imaging (MRI) scans.

Those scans confirmed the heart chamber ballooning, and doctors could also see that in 81% of cases the heart muscle itself was also very swollen.

After the diagnoses were confirmed, patients were treated with drugs to manage blood pressure and heart failure.

Eight patients died during the study, but the vast majority made a full recovery. Their scans looked normal after six months.

"You can look very sick," Wittstein says. "The good news is that you are left with a normal heart muscle by the time all is said and done."

Even though people who have broken heart syndrome nearly always bounce back, doctors say it would be a mistake for someone to try to self-diagnose the condition, since stress can also cause true heart attacks.

"You've got to remember 98% of the time, when you have a heart-attack-like syndrome, it's going to be a real heart attack," Hanna says. "This is not rare, we see this a lot, but we see garden variety coronary artery disease and heart attacks way more than this."